Fig. 5. Gene regulation in Alx4, Cart1, Gli3 and Tbx15 compound mutants. (A-D) Pax1 expression in E10.5 wild-type (A), Tbx15^–/– (B), Gli3^–/– (C) and Tbx15/Gli3 double mutant (D) forelimb buds. Note the downregulation of Pax1 expression in the mutants. (E-L) Pax1 expression in E10.75 wild-type (E,I), Alx4^–/– (F), Cart1^–/– (G), Alx4^+/–/Cart1^–/– (J) and Alx4^–/–/Cart1^–/– (H,K,L) forelimb buds. (E-H) Dorsal views of the limb buds. Note the downregulation of Pax1 in Alx4/Cart1 compound mutants (H). (I-L) Ventral view of the limb buds. Yellow arrowhead indicates the shift of Pax1 expression in Alx4^+/–/Cart1^–/– (J) and Alx4^–/–/Cart1^–/– (K,L) mutants. (M-P) Pax1 expression in wild-type (M,O) and Alx4/Cart1 mutant (N,P) fore- and hindlimb (HL) buds at E11.5. Yellow arrowhead (N,P) indicates the shift of Pax1 expression. (Q-T) In situ hybridization on serial transversal sections at E10.5 of wild-type (Q,S) and Alx4/Cart1 mutant (R,T) embryos. (Q,R) Pax1 expression is downregulated in Alx4/Cart1 mutants. (S,T) Pax3 is abnormally expressed in the mesenchyme just adjacent to the surface ectoderm in Alx4/Cart1 mutants (black arrow in T). (U,V) Whole-mount in situ hybridization with Pax3 probe of E10.5 wild-type (U) and Alx4/Cart1 mutant (V) limb buds. Red arrowhead (V) indicates Pax3 expression that is shifted towards the antero-proximal region of the limb bud. (W,X) Expression of Scleraxis (Scx) in E10.5 wild-type (W) and Alx4/Cart1 mutant (X) limb buds. Green arrowhead (X) indiactes the shift of Scx expression in the Alx4/Cart1 mutant. (Y) Schematic representation of the expression patterns of Pax1, Pax3 and Scleraxis in wild type, and in Alx4/Cart1 and Tbx15/Gli3 compound mutants.